JPH11106258A - Baxsr1-xti03-y target material for sputtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a target material for sputtering composed of a sintered compact, represented by Bax Sr1-x TiO3-y enabling the production of a thin film hardly containing particle defects and simultaneously improving the mechanical strength. SOLUTION: This target material for sputtering has >=97% relative density of a sintered compact and <=3 μm average crystal grain diameter of the sintered compact in the target material for the sputtering composed of the sintered compact of a perovskite type compound oxide represented by the formula Bax Sr1-x TiO3-y [0<=(x)<1 and 0<=(y)<0.5]. The target material for the sputtering is produced by baking a synthetic powder of the Bax Sr1-x TiO3-y having <=1 μm average grain diameter according to a hot-pressing method, a method for using the hot-pressing method and a hot isostatic pressing(HIP) in combination and a method for using a sintering method under atmospheric pressure and the HIP in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a MOS-ULSI
The present invention relates to a sputtering target material represented by a composition formula of Ba _x Sr _1-x TiO _3-y used when forming a high dielectric capacitor thin film of the present invention by a sputtering method. The present invention relates to a sputtering target material that enables the production of a small number of thin films and at the same time improves mechanical strength.

[0002]

2. Description of the Related Art In recent years, the use of a thin film of SrTiO ₃ having a high dielectric constant or a Ba _x Sr _{1 -x} TiO ₃ in which a part of the Sr site is replaced with Ba has been studied as a capacitor of a semiconductor memory. One of the methods for forming such a high dielectric thin film is a sputtering method using a target. SrTiO ₃ or Ba _x Sr _1-x TiO ₃ in which a part of the Sr site is replaced with Ba is used. In addition, it is difficult to obtain a dense sputtering target because the material is liable to cause abnormal grain growth during firing, and the crystal grain size is 20 μm due to the development of abnormal grain growth when firing at high temperature for densification. The above sintered body structure is obtained.

When such a sintered body is used as a sputtering target, many defects called particles (clustered particles emitted from the target) are generated on the formed thin film, and the yield is greatly increased. There was a problem that it decreased. Further, when a sintered body is machined to a target size, a sintered body having a low density or a sintered body having a large crystal grain size has low mechanical strength, and thus has problems such as a reduction in yield and contamination by impurities.

[0004]

The object of the present invention is to provide a compound of the general formula Ba _x Sr _1-x TiO _3-y (where 0 ≦ x <1, 0 ≦
y <0.5) a sputtering target material comprising a perovskite-type composite oxide sintered body represented by the following formula:
An object of the present invention is to make it possible to produce a thin film having very few particle defects, and at the same time to improve its mechanical strength. In the prior art, those that directly address such problems of particle defects and mechanical strength in a sputtering target material composed of a perovskite-type composite oxide sintered body represented by Ba _x Sr _1-x TiO _3-y Absent.

[0005]

The inventors of the present invention have studied to solve the above-mentioned problems and found that Ba _x Sr _{1- x}
The relative density of the sintered body represented by the composition formula of TiO _3-y is 97
% Or more, and the crystal grain size of the sintered body is 3 μm or less, the particle defect becomes 1 / cm ² or less,
Further, they have found that the yield by machining is significantly improved. Normally, firing at high temperature for densification results in a sintered body structure with a large crystal grain size due to the development of abnormal grain growth, but the present invention simultaneously realizes these conflicting requirements through appropriate control of the manufacturing method. Was successful.

Thus, the present invention provides a compound of the general formula Ba _x Sr
_1-x TiO _3-y (however, 0 ≦ x <1, 0 ≦ y <0.5)
In the sputtering target material composed of a perovskite-type composite oxide sintered body represented by the following formula, the relative density of the sintered body is 97% or more, and the average crystal grain size of the sintered body is 3 μm or less. Provided is a sputtering target material characterized by the following.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a target material having the above-described relative density and average grain size characteristics will be described in detail. Starting materials include BaCO ₃ and / or SrCO _{3 having} a purity of 3N or more and an average particle size of 1 μm or less, T
Use iO ₂ powder. These raw material powders are weighed so as to have a predetermined composition, wet-mixed through a medium such as alcohol, and then subjected to thermal synthesis at 850 to 1000 ° C. to have Ba _x Sr _1-x TiO ₃ having an average particle size of 1 μm or less. Obtain a synthetic powder.

[0008] The firing method includes a hot press method and a hot press method.
There are a method using IP together and a method using both normal pressure sintering and HIP. In the case of the hot pressing method, Ba _x Sr _1-x TiO ₃ having an average particle size of 1 μm or less obtained by thermal synthesis.
The powder is placed in an Ar atmosphere at 1250-1350 ° C., 15-3
By firing at 0 MPa, a sintered body having a relative density of 97% or more and a crystal grain size of 3 μm or less can be obtained. At this time, if the sintering temperature exceeds 1350 ° C., the density increases, but abnormal grain growth occurs, resulting in a crystal structure having a grain size of 20 μm or more or a mixed structure of abnormal grains and fine grains, resulting in a decrease in mechanical strength. If the firing temperature is lower than 1250 ° C., a sintered body having a relative density of 97% or more cannot be obtained.

When the hot press method and the HIP are used together, the hot press temperature is set to 1180 to 1350 ° C. to make the pore form on the sintered body surface closed pores.
By performing the HIP treatment at 〜1350 ° C. and 50 MPa or more, a sintered body having a relative density of 97% or more and a crystal grain size of 3 μm or less can be obtained. In order to obtain a sintered body having a relative density of 97% or more by the normal pressure sintering method, a long holding time at 1400 ° C. or more is required, and abnormal grains are remarkably developed. Therefore, at a firing temperature of 1350 to 1450 ° C., a sintered body having a relative density of 90 to 94% and pores on the surface of the sintered body being closed pores is produced by an appropriate holding time, and 1250 to 1350
A sintered body having a relative density of 97% or more and a crystal grain size of 3 μm or less can be obtained by performing the HIP treatment at 50 ° C. or more at 50 ° C. In addition, during the HIP treatment, the sintered body is exposed to a low-oxygen atmosphere at a high temperature, so that a Ba _1-x Sr _x TiO _3-y sintered body having electrical conductivity is obtained.

Thus, the general formula Ba _x Sr _1-x TiO
_3-y (where 0 ≦ x <1, 0 ≦ y <0.5) In a target material for sputtering a perovskite-type composite oxide sintered body, the relative density of the sintered body is 97% or more and The crystal grain size of the sintered body can be 3 μm or less. The obtained sintered body is machined into a shape of a sputtering target material.

Ba _x Sr _1-x TiO _3-y having a relative density of 97% or more and a crystal grain size of 3 μm or less prepared by the above-mentioned method.
(However, the sintered body represented by the composition of 0 ≦ x <1, 0 ≦ y <0.5) has a remarkably improved yield when processed into a sputtering target, and is used as a sputtering target. Ba _x Sr _1-x TiO ₃
In the thin film, the number of particle defects becomes 1 / cm ² or less, and the production yield of the semiconductor memory is remarkably improved.

[0012]

EXAMPLES Examples and comparative examples of the present invention and test results will be described below.

(Example 1) A wet ball mill in which BaCO ₃ powder, SrCO ₃ powder and TiO ₂ powder having a purity of 4N and a particle size of 1 μm or less were mixed in a molar ratio of 1: 1: 2, and ethanol was used as a medium. Mixing was performed by the method. After the mixed slurry is dried, thermal synthesis is performed at 1000 ° C. in the air to form Ba.
_0.5 Sr _0.5 TiO ₃ synthetic powder was obtained. An organic binder was added as a molding aid to this synthetic powder, pre-molded using a mold, and then fully molded by CIP. In order to remove the added organic binder, a degreasing treatment was performed in the air, followed by baking in the air at 1370 ° C. for 2 hours to obtain a preliminary sintered body having a relative density of 93%. This sintered body is further subjected to 130
HIP treatment was performed at 100 MPa for 1 hour at 0 ° C., and the density, structure, and transverse rupture strength of the sintered body were measured. Next, the sintered body produced in the same manner was machined into the shape of a sputtering target material (diameter: 4 inches, thickness: 6 mm), and the substrate temperature: 5
50 ° C., sputtering gas pressure: Ar = 0.3 Pa, O ₂ =
A (Ba, Sr) TiO ₃ thin film was formed by RF sputtering under the conditions of 0.1 Pa and a sputtering power density of 3 W / cm ² , and the number of particles on the thin film was measured. Table 1 shows the results.

The sintered body obtained in Example 1 had a relative density of 99.2% and a fine structure having a crystal grain size of 2.3 μm. The bending strength due to the three-point bending was 220 MPa, and there was no crack in the target during machining. The number of particles in the thin film formed by using these targets was as small as 0.2 particles / cm ² .

Example 2 Ba _0.5 Sr _0.5 TiO ₃ powder synthesized under the same conditions as in Example 1 was used at 1300 ° C. and 30 ° C.
A sintered body hot-pressed under the conditions of 30 minutes and 30 MPa was produced, and the same evaluation as in Example 1 was performed.

The sintered body obtained in Example 2 had a relative density of 98.9% and a fine structure having a crystal grain size of 1.6 μm. The transverse rupture strength by three-point bending was 219 MPa, and there was no cracking of the target during machining. The number of particles in a thin film formed using these targets was as low as 0.4 particles / cm ² .

(Comparative Example) Ba synthesized under the same conditions as in the example
_{Using 0.5} Sr _0.5 TiO ₃ powder, a sintered body fired at 1300 ° C. for 10 hours and at 1500 ° C. without holding was obtained. The obtained sintered body was heated at 1300 ° C. for 1 hour for 10 hours.
HIP was performed under the condition of 0 MPa, and the density, structure, and transverse rupture strength of the sintered body were measured. Further, these sintered bodies were machined into a sputtering target under the same conditions as in the example, and a film was formed.
The number of particles in the thin film was measured. Table 1 shows the results.

The sintered body fired at 1300 ° C. for 10 hours had a very fine average particle size of 1 μm or less.
The relative density after HIP is as low as 88%, and the transverse rupture strength is 100M.
At Pa or less, cracks were observed during target processing. The relative density of the sintered body fired at 1500 ° C. was relatively high at about 97%, but the average particle size was 68 μm.
m, and the transverse rupture strength was as low as about 140 MPa.
The number of particles in a thin film formed using these target materials was as large as 4 particles / cm ² or more.

[0019]

[Table 1]

[0020]

As described above, according to the present invention,
The relative density of the target material represented by the composition formula of Ba _x Sr _1-x TiO _3-y is 97% or more, and the average particle size is 3 μm.
By performing the following, the mechanical strength can be improved, the target processing yield can be improved, and contamination during processing can be prevented. Further, by using this target, a thin film having very few particle defects can be obtained by a sputtering method, and the yield and reliability of the semiconductor memory can be improved.

Claims (1)

[Claims] 1. A sputtering method comprising a perovskite-type composite oxide sintered body represented by the general formula Ba _x Sr _1-x TiO _3-y (where 0 ≦ x <1, 0 ≦ y <0.5) A target material for sputtering, wherein the relative density of the sintered body is 97% or more, and the average crystal grain size of the sintered body is 3 μm or less.